1892] MARYLAND ACADEMY OF SCIENCES. 227 



estuary of the James, I should expect to find colonies on 

 the older landings in the region of Lower Brandon, James- 

 town Island, and Carter's Grove. The waters of the 

 Chickahominy, which also Mr. Darton and myself tra- 

 versed from the mouth well toward the head of tide, seem 

 nearly as favorable for the colonies as those of the Pamun- 

 key, and for similar reasons. 



I have made a few observations relative to the range of organisms, 

 whicli are accessible to the colonies as food. 



Our Cordylophora appears to be exclusively carnivorous. Its tentacles 

 are by far less sentitive than those of the fresh-water Hydra, and their 

 movements proportionally sluggish. Contact of a comparatively large 

 form is necessary to stimulate them to action. Microscopic animals, 

 and even many visible to the naked eye, swim against their tentacles with 

 impunity. The smallest prey which I have seen the hydroids capture 

 and devour were rotifers about one-third the dimensions of Pldlodiiia 

 roseola, and a form quite readily visible without a lens. 



Both at Cinder Cove and in the Patapsco a small, but extremely active 

 and fierce nematode frequents the stems and branches of the colonies. 

 I liave often seen them wriggling along individual stems among the 

 foreign particles, diatoms, etc., commonly adhering to their surf ace. They 

 do not appear to appreciate in the least the danger of being capturedby 

 the voracious hydranths which tip the plant-like stems and branches of 

 the animal forest which they inhabit, and commonly proceed directly 

 into contact with their tentacles. After a desperate struggle (in which 

 the nematode lacerates with its powerful jaws the ectoderm of its cap- 

 tor's tentacles and body-Avall, but without avail) the worm is usually 

 forced alive and writhing with pain from the nettle cells with which 

 its body is beset, into the hydroid's enormously enlarged mouth, and 

 finally into its stomach. At Cinder Cove these worms appear to con- 

 stitute no inconsiderable portion of the hydroid's food. Here I also 

 observed the devouring of an insect larva fully three times the length 

 of ahydranth. The posterior extremity of the larva projected far out 

 of the mouth of its devourer, being securely held in place by her ten- 

 tacles. 



Last summer, at Curtis Bay, I found attached to Nitella, quantities of 

 which the fishermen had gathered from the tide water at that point in 

 which to pack their soft crabs, numerous rotifers apparently the same in 

 every respect as Fhilodina roseola of our cemetery urns, save in the absence 

 of the red color from the digestive organs. I had previously offered the 

 latter to a detached hydranth of Cordylophora, and three of the former 

 were devoured in quick succession. I therefore concluded that in Cur- 

 tis Creek this tide-water Philodina probably also serves as food for the 

 hydroids. 



